I.MX6 U-Boot mkconfig hacking

/****************************************************************************
*                     I.MX6 U-Boot mkconfig hacking
* 声明：
*     本文主要是为了知道U-Boot中的mkconfig是如何工作的，是如何将配置
* 中的内容进行汇总，同时又将这些内容放在了什么地方。
*
*                                       2015-12-19 深圳 南山区平山村 曾剑锋
***************************************************************************/

\\\\\\\\\-*- 目录 -*-//////////
|  一、参考文档：
|  二、Makefile
|  三、mkconfig
|  四、include/config.h
|  五、include/config.mk
------------------------------

一、参考文档：
1. $(@:_config=)什么意思？ http://blog.csdn.net/zbffff/article/details/18991145 2. U-BOOT Makefile注释 http://wenku.baidu.com/view/ff14f319227916888486d7cb.html 3. makefile中的@ http://www.cnblogs.com/lihaiping/archive/2013/03/20/makefile.html 4. Makefile中常用的函数 http://linux.chinaunix.net/techdoc/develop/2009/07/09/1122854.shtml 5. U-Boot移植（二）——U-Boot编译过程分析（2） http://blog.csdn.net/wafx1314/article/details/11260041 6. 请教linux make make clean make all 的具体用法 http://zhidao.baidu.com/question/129692720.html 
二、Makefile
......
SRCTREE    := $(CURDIR)
......
MKCONFIG   := $(SRCTREE)/mkconfig
export MKCONFIG
......
mx6solo_sabresd_config            \
mx6solo_sabresd_mfg_config        \
mx6solo_sabresd_android_config        \
mx6dl_sabresd_config            \
mx6dl_sabresd_mfg_config        \
mx6dl_sabresd_android_config            \
mx6q_sabresd_config            \
mx6q_sabresd_android_config             \
mx6q_sabresd_mfg_config            \
mx6q_sabresd_iram_config    : unconfig
@[ -z "$(findstring iram_,$@)" ] || \
{ echo "TEXT_BASE = 0x00907000" >$(obj)board/freescale/mx6q_sabresd/config.tmp ; \
echo "... with iram configuration" ; \
}
@$(MKCONFIG) $(@:_config=) arm arm_cortexa8 mx6q_sabresd freescale mx6
......

三、mkconfig
#!/bin/sh -e

# Script to create header files and links to configure
# U-Boot for a specific board.
#
# Parameters:  Target  Architecture  CPU  Board [VENDOR] [SOC]
#
# (C) 2002-2006 DENX Software Engineering, Wolfgang Denk <wd@denx.de>
#

APPEND=no    # Default: Create new config file
# 开发板的名字
BOARD_NAME=""    # Name to print in make output

# 使用while循环和case进行命令行参数提取，很不错的处理方式
while [ $# -gt 0 ] ; do
case "$1" in
--) shift ; break ;;
-a) shift ; APPEND=yes ;;
-n) shift ; BOARD_NAME="${1%%_config}" ; shift ;;   # %%去除$1字符串中的_config
*)  break ;;
esac
done

# 如果上面的命令行参数都没有，那么$1就是开发板的名字
[ "${BOARD_NAME}" ] || BOARD_NAME="$1"

# 参数个数小于4个或者大于6个，直接退出，比较奇怪的是，为什么不放在前面进行判断呢
[ $# -lt 4 ] && exit 1
[ $# -gt 6 ] && exit 1

# 显示提示信息
echo "Configuring for ${BOARD_NAME} board..."

#
# Create link to architecture specific headers
#
# 如果编译出来的目录和源代码目录不一样，那么执行以下内容
if [ "$SRCTREE" != "$OBJTREE" ] ; then
mkdir -p ${OBJTREE}/include         # 创建include目录
mkdir -p ${OBJTREE}/include2        # 创建include2目录
cd ${OBJTREE}/include2              # 进入include2目录
rm -f asm                           # 防止asm已经存在
ln -s ${SRCTREE}/include/asm-$2 asm # 重新软链接到固定的位置$2(arm)平台
LNPREFIX="../../include2/asm/"
cd ../include
rm -rf asm-$2
rm -f asm
mkdir asm-$2
ln -s asm-$2 asm
else
cd ./include
rm -f asm
ln -s asm-$2 asm        # $2=arm
fi

# 删除include/asm-arm/arch这个软链接
rm -f asm-$2/arch

# $6等于mx6
if [ -z "$6" -o "$6" = "NULL" ] ; then
ln -s ${LNPREFIX}arch-$3 asm-$2/arch
else
ln -s ${LNPREFIX}arch-$6 asm-$2/arch
fi

if [ "$2" = "arm" ] ; then
rm -f asm-$2/proc
ln -s ${LNPREFIX}proc-armv asm-$2/proc
fi

#
# Create include file for Make
#
echo "ARCH   = $2" >  config.mk     # $2=arm
echo "CPU    = $3" >> config.mk     # $3=arm_cortexa8
echo "BOARD  = $4" >> config.mk     # $4=mx6q_sabresd

# $5=freescale
[ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk

# $6=mx6
[ "$6" ] && [ "$6" != "NULL" ] && echo "SOC    = $6" >> config.mk

#
# Create board specific header file
# APPEND=no
if [ "$APPEND" = "yes" ]    # Append to existing config file
then
echo >> config.h
else
> config.h        # Create new config file
fi
# 原来我们可以在在这个文件里查看config文件
echo "/* Automatically generated - do not edit */" >>config.h
# $1=mx6dl_sabresd_android
echo "#include <configs/$1.h>" >>config.h
echo "#include <asm/config.h>" >>config.h

exit 0

四、include/config.h
/* Automatically generated - do not edit */
#include <configs/mx6dl_sabresd_android.h>
#include <asm/config.h>

五、include/config.mk
ARCH   = arm
CPU    = arm_cortexa8
BOARD  = mx6q_sabresd
VENDOR = freescale
SOC    = mx6

六、总结：
从上面的情况可知，如果要在board目录下新建一个开发板<board_name>目录，则在include/configs目录下也要建立一个对应的<board_name>文件，里面存放的就是开发板<board_name>的配置信息。这里目前没有验证。